But the most important startup he’s advised is much closer to home: his 10-year-old son, Owen, a budding inventor and entrepreneur.

At the Nannarone home in suburban Boston one recent Sunday, father and son discuss Owen’s latest invention, a golf tee that records the speed and angle of the club to analyze a swing. Len is outgoing and energetic, but Owen remains quiet, his eyes partially hidden by his shock of brown hair. He deftly peels the protective cover off an alkaline battery, as if shelling a peanut, while dad explains the impetus for their design.

See, Owen takes golf lessons, and his coach uses a swing analyzer that’s just too big and clunky for Owen. “They have these huge machines,” Owen says, momentarily taking his eyes off the battery. Len chimes in. “He said, ‘Dad, can’t they put all that stuff in a golf tee?’”